Here's another vote for Westley's. Never had a problem staining paint, but I scrub and rinse while it's still wet. It does have bleach in it and can stain paint, and aluminum, too, if you let it dry before rinsing, especially in hot sunlight.

For really stubborn dirt/stains, I scrub with 0000-grade steel wool; otherwise, a soft-bristle scrub brush works fine.